We've been using Google's voice-guided driving directions on an Android phone since October, but we didn't have too many equivalent apps to compare it with until Microsoft released its own voice navigation service for Bing last week for Windows phones.
We took Bing on a few test drives against Google's map navigation, all in the San Francisco Bay Area. Both apps will likely eventually get you where you want to go, but both exhibited overly creative directions and produced their own frustrating errors.
What we liked
We immediately noticed Bing's less tinny-sounding directions bot. Sure, "she" still sounds robotic, but less so than Google's navigatrix. We also appreciated how the Bing app "bings" before sounding off the next direction. The chime was a natural and unintrusive interruption to signal that voice guidance is imminent. It would have been nice if Bing also chimed to indicate that it's time to make a left or right turn, as Magellan's GPS units do, but that's a more minor quibble.
What we didn't like
Bing was the more navigationally flawed app in our tests compared with Google's navigation. Google's maps also have more features and options; for example, a street-level and bird's eye perspective of the map.
Within our first two test runs, Bing thrice dispensed misdirections that didn't correlate to the real world, including directing us to circle around a neighborhood even when we were on the same street as the destination address. There were also more trivial directional errors that turned up in subsequent testing.
We should note that commercial GPS navigators also run into the same pitfalls we noticed with Bing's navigation--like offering directions too early or too late and temporarily dropping GPS fixes (specifically within urban canyons)--so we can't dump all our blame on Bing, especially for issues that actually generate from the hardware and environmental access to GPS signal, and not from the software itself.
What else Google does better than Bing
On an absolute basis, we prefer Google Maps navigation to Bing's naviagion for its more faithful directions and more numerous map views, but also for its interface design. It's not exactly a fair fight. Specs-wise, the HTC Incredible on which we tested Google's Android-enabled navigation outclasses the Windows Mobile HTC Pure loaded with Bing. Yet resolution and screen size aside, Google's navigation visuals--with its sharper corners, larger characters, and higher-impact color palette--provide an easier-to-read experience that's essential for drivers who might glance at the app to get their bearings.
Although Bing has a ways to go to catch up to Google's overall quality, if you've got a Windows phone, the "pro" of free voice navigation outweighs the service's cons. As with similar voice guidance software, Bing fetches directions after you add an address or location, pick a place on a map, select from favorite locations, and choose destinations-by-address book contacts--and it'll automatically reroute if you've missed a turn.
Just take Bing's voice guidance, like all navigation units, with a grain of salt.